Re: [fluka-discuss]: muon + mgdraw

From: Francesco Cerutti <Francesco.Cerutti_at_cern.ch>
Date: Mon, 25 Sep 2017 22:03:48 +0200

Dear Andrea,

Giuseppe's answer makes clear that USERDUMP/mgdraw is an advanced scoring,
to be properly customized on user's responsibility, and is the last tool
to use in order to tackle a problem. One should first understand what is
going on through the built-in scoring options, such as USRYIELD, USRTRACK,
USRBIN, USRBDX, which may also be enough depending on the actual needs.
Moreover, the use of biasing implies to handle yourself the statistical
weights, that instead in the built-in scoring are automatically accounted
for.

I guess that your muon production comes from bremsstrahlung photons, you
ask for mu+/mu- pair production (as only production mechanism), but also
photon nuclear interactions (through further pion decay) may be relevant.
For this you need PHOTONUC with SDUM empty. Forget about ELECTNUC that is
actually not available in the released version and plays a role for thin
targets.

I'm not sure that the use of leading particle biasing (EMF-BIAS) is a good
idea, since this way you just tend to kill bremsstrahlung photons. On the
other hand, tracking electrons and photons down to 10 keV and 1 keV,
respectively, has nothing to do with muons and makes your CPU time
explode.
I do not understand either the use of RADDECAY, since you do not seem to
be interested in radioactive nuclei.

Concerning muon reinteractions, MUPHOTON and PAIRBREM are useless with
PRECISIO, since the respective processes are already on.

So I suggest you clean your input focusing on the relevant physics levers,
including photon interaction length biasing (with LAM-BIAS for nuclear
interactions and directly PHOTONUC for mu+/mu- pair production), and put
an instructive USRYIELD scoring at the exit of your lead target.

Kind regards

Francesco

**************************************************
Francesco Cerutti
CERN-EN/STI
CH-1211 Geneva 23
Switzerland
tel. +41 22 7678962
fax +41 22 7668854

On Mon, 25 Sep 2017, Giuseppe Battistoni wrote:

> Hi Andrea
> some partial answers.
> I leave to others the question of EMF-BIAS because there are more
> important things and I will concentrate on the use of mgdraw.
>
> Such a topic is not easy at all and I'll try to give you some hints.
>
> You are placing the write statements in the USDRAW section (actually these
> sections technically are called ENTRY), and you are not using the proper
> variables.
> In this entry JTRACK is the code of the particle interacting at coordinates
> XSCO, YSCO, ZSCO. It has nothing to do with particles created in that
> interaction.
> Looping on NP you must scroll the arrays of common Genstk
> [ see in $FLUPRO/flukapro the content of (GENSTK) ] and you will select
> muon by asking for kpart(ip) = 10 or 11. Look carefully at the other arrays
> of GENSTK common for all kinematical infos.
>
> JTRACK, ETRACK, XTRACK etc are variables of the common (TRACKR) in which
> are copied, one at a time, the variables of transported particles, taking
> them from GENSTK. You will use them in other Entries of Mgdraw. For instance
> in the BXDRAW entry, those variables will identify the running particle
> during transport at the moment in which a boundary between regions is
> crossed. USDRAW Entry instead "captures" the moment in which particles are
> created, not the action of transport.
> Individual particle transport can be followed in the main initial part of
> mgdraw.f using the variables of (TRACKR) common block.
>
> I don't know if this is clear enough...
>
> Ciao
> Giuseppe
>
> On 25/09/2017 16:47, andrea russomando wrote:
>> Dear FLUKA experts
>>
>> Iím studying the interaction of an electron beam with a lead target
>> I would like to record all the muons created, and save the variables needed
>> to reconstruct their kinematic
>>
>> For this purpose Iím using a modified version of mgdraw
>>
>> I never used it before, so I have some doubts
>>
>> 1) Am I using the right cards?
>> I donít know if Iím using in the right way the card EMF-BIAS (the manual
>> suggests to be very careful in the mixing of bias and dump) and I donít
>> know if I should activate the card photonuc (type electrnuc).
>> If this card is enable seems to me that the muons are produced at rest,
>> while otherwise have very high energy (I attached the two different dumps)
>> 2) I canít understand the results of the dump
>> It seems that the same particle is written more than once in the stack
>> Also I always obtained Ntrack=0 (from what I understand it means a local
>> energy deposition), even though Iím using a low threshold in the card
>> PART-THR
>>
>> Thanks in advance
>> andrea
>>
>
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Received on Mon Sep 25 2017 - 23:46:20 CEST

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